100% GE silicone is best for a joint that will move that much. There must be good adhesion on the sides and it can stick to nothing in the middle which is best accomplished with a backer rod if it will stay in place long enough to give the sealant an hour glass shape. I would try to match the color of the brick not the window because it will be a mess.

But it will only be temporary since the window doesn't really fit in the opening. For a proper sealant joint the window must overlap the brick about an inch and there should be about a 1/4" joint for the sealant. You might have to add some small aluminum angles to the front of the window to create that kind of joint or tear it out and start over.

I only saw the white 100% GE silicone in the Home Depot. Do you know where I can find the red 100% GE silicone to match the bricks? In addition, can you see what material that the builder to apply to fill the joint between the window frame and wall and among the bricks? Picture

It looks like mortar to me and I would assume it will fall out eventually.

Here is a link that might be useful: silicone color